Geography Project - Volacanoes

“Are volcanoes FRIENDS or FOES of human beings ??”

Section 2 - How are volcanic eruptions predicted

Sunday, 20 March 2011 || 01:47

Section 2: How are volcanic eruptions predicted

Volcanoes are mostly unpredictable. There are, however, some means of detection and prediction, both natural and scientific.

Scientists have developed various instruments to measure predictors of volcanic eruption. The ground may tilt slightly before an eruption; a tiltmeter measures this activity. Seismographs, commonly used in recording earthquakes, can also be used to gauge the rumblings that sometimes come before an eruption.

A seismometer (or seismograph) is a sensor that detects the intensity of earthquakes caused by magma that is moving. Since magma gives off electric currents, electric meters are used tospot rising magma levels by measuring its electric current. Gravimeters can also detect flowing magma. Scientists also take temperatures and gauge gas by using a Landsat satellite. The satellite uses infrared sensors to detect temperatures and changes in volcanoes. Aircraft monitors the amount of gas released from the ground. An increase in sulfur dioxide and other gases usually means that there could be volcanic eruptions. The tiltmeter is a sensor that uses a laser beam to find the rising or lowering of magma levels by measuring changes in ground elevation. GPS (Global Positioning System) is a method to determine position of locations on Earth. It uses satellites that broadcast a signal and receivers that pick up and record the signal. GPS uses the relationship between velocity, distance, and time (velocity equals distance divided by time). With GPS, the velocity is the speed of light. Knowing the velocity and time (and the position of the satellite) allows the distance to be calculated. As magma moves up into a volcano the volcano swells and distances between points on the volcano increases (think of dots on a balloon) and the elevation at specific points increases. Such a change is a common occurrence prior to an eruption.

Volcanologists use these instruments to successfully predict eruptions which saves many lives.

Close observance of the area around a volcano can provide important signals. Clouds of steam or smoke may arise from the volcano’s crater. The ground may rumble. There may be minor shudders or earthquakes.

The increased temperature of nearby streams, springs, and even surface rocks may give a clue. Rock slides or avalanches from the volcano’s cone or slopes provide evidence of possible eruption. However, all these things may happen without further volcanic activity.

Rising magma distorts Earth’s natural electric currents and magnetic field. A restivity meter and a magnetometer note these changes. Thermometers register changing temperatures in the surrounding environment, which may precede volcanic eruptions.

Despite all of these ways to monitor volcanoes, eruptions and explosions are difficult to predict.